The motor has a thermal switch in it wired to a starter. Trying to think how well these will work on a phase loss.If the motor says on the nameplate that it is”Thermally Protected” or in some other way indicates that, you don’t need an external OL relay. If it has embedded thermal sensors that use resistance (RTDs or PTC thermistors), you must have some sort of relay that interfaces with them. Those are usually way more expensive than an OL relay.
The motor has a thermal switch in it wired to a starter. Trying to think how well these will work on a phase loss.
Past experiences have shown they fail open years before the motor has actual issue. Also they have been used in conjunction with an overload block. Not this time.
Had a lot of them on 2 to 10 HP Explosion proof motors in a starch molding room at a candy company years ago. Never had touble with them but had to watch when you had motors rewound. Some shops would remove them and not say anything. We always used overloads on these motors.Is an internal thermal allowed for overcurrent protection of a motor? 25 HP 480. Mfg supplied starter.